3,5-Lutidine pentaaqua sulfate complexes of first-row transition metals: [M(3,5-lutidine)(H2O)5]SO4, with M = Mn, Co, Ni, and Zn

The structures of four metal 3,5-lutidine pentaaqua sulfates (Mn, Co, Ni, Zn) are presented and are shown to be isostructural.


Chemical context
Metal-pyridine sulfate complexes have been reported in the literature since the 1880s (Jørgensen, 1886;Reitzenstein, 1898;Manke, 2021), though an extensive and systematic look at the crystal structures of this class of compounds has never been undertaken. In recent years, our laboratory began looking at the structures of first-row transition-metal-pyridine sulfate complexes, first with the parent pyridine (Park et al., 2019;Pham et al., 2018;Roy et al., 2018) and then with picoline ligands (Park et al., 2022;Pham et al., 2019). In our efforts to examine the structural diversity of this class of compounds, we recently expanded to look at lutidine ligands. Herein we report four isostructural first-row transition-metal complexes of 3,5-lutidine.

Figure 2
The crystal packing of 3,5-lutidine pentaaqua zinc sulfate (4). Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are shown as dashed lines andinteractions are shown as bold dashed lines. Hydrogen atoms not involved in hydrogen bonding are omitted for clarity.

Synthesis and crystallization
A metal sulfate (44 mg of MnSO 4 ÁH 2 O, 44 mg of CoSO 4 Á-7H 2 O, 217 mg of NiSO 4 Á6H 2 O, 33 mg of ZnSO 4 Á7H 2 O) was dissolved in five drops of water and 2.5 mL of 3,5-lutidine. The resulting solution was heated to 338-343 K for twelve hours and allowed to cool slowly to room temperature producing single crystals suitable for X-ray diffraction. The manganese crystals formed as colorless blocks, the cobalt crystals formed as pink blocks, the nickel crystals formed as pale-green plates, and the zinc crystals formed as colorless blocks.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 7. The water hydrogen atoms H1, H2A, H2B, H3A, and H3B were found in difference-Fourier maps. These hydrogen atoms were refined isotropically, using DFIX restraints with O-H distances of 0.78 (1) Å . Isotopic displacement parameters were set to 1.5 U eq of the parent oxygen atom. All other hydrogen atoms were placed in calculated positions Isotropic displacement parameters were set to 1.2 U eq of the parent aromatic carbon atoms and 1.5 U eq of the parent methyl atoms.

Pentaaqua(3,5-dimethylpyridine-κN)manganese(II) sulfate (1)
Crystal data  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )

Pentaaqua(3,5-dimethylpyridine-κN)cobalt(II) sulfate (2)
Crystal data  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.43 e Å −3 Δρ min = −0.29 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Pentaaqua(3,5-dimethylpyridine-κN)nickel(II) sulfate (3)
Crystal data [Ni(C 7  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.44 e Å −3 Δρ min = −0.33 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

sup-12
Acta Cryst. (2023). E79, 648-651 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )